* {
    padding: 0;
    margin: 0;
}

body {
    height: 100vh;
    background-image: url('images/violin.png');
    background-size: cover;
}

.container {
    width: 400px;
    height: 600px;
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    background-color: rgba(32, 32, 32, .9);
    border-radius: 10px;
    user-select: none;
    overflow: hidden;
    box-shadow: 5px 5px 5px rgba(32, 32, 32, .9);
}

.up-screen {
    margin-top: 40px;
    height: 80px;
}

.up-screen::before {
    position: absolute;
    top: 20px;
    left: 20px;
    content: '计算器';
    color: white;
    font-size: 20px;
}

.up-screen::after {
    position: absolute;
    top: 60px;
    left: 5%;
    width: 90%;
    height: 1px;
    background-color: rgba(255, 255, 255, .3);
    content: '';
}

.up-screen span {
    position: absolute;
    color: rgba(255, 255, 255, .6);
    line-height: 30px;
    right: 10%;
    font-size: 20px;
    margin-top: 50px;
    user-select: text;
    transition: .2s;
}

.down-screen {
    height: 80px;
    line-height: 80px;
}

.down-screen span {
    position: absolute;
    color: white;
    line-height: 40px;
    right: 10%;
    font-size: 32px;
    margin-top: 20px;
    user-select: text;
    transition: .2s;
}

.keyboard {
    height: 400px;
    padding: 5px;
    text-align: center;
}

button {
    width: 72px;
    height: 60px;
    margin: 2px 0;
    color: white;
    border: 0;
    border-radius: 6px;
    font-size: 20px;
    cursor: pointer;
    opacity: .8;
}

.number {
    background-color: rgb(59, 59, 59);
}

.number:hover {
    background-color: rgb(50, 50, 50);
}

.number:active {
    background-color: rgb(38, 40, 45);
}

.operator {
    background-color: rgb(50, 50, 50);
}

.operator:hover {
    background-color: rgb(59, 59, 59);
}

.operator:active {
    background-color: rgb(50, 50, 50);
}

#equal {
    background-color: rgb(158, 200, 210);
    color: black;
}

#equal:hover {
    background-color: rgb(145, 183, 193);
}

#equal:active {
    background-color: rgb(132, 166, 175);
}

#statement {
    position: fixed;
    left: 20px;
    bottom: 20px;
    font-size: 20px;
    font-family: 'Segoe Print', 'Microsoft YaHei UI', Consolas;
    color: white;
    cursor: default;
}

.github-corner {
    fill:rgb(68, 69, 71);
    color:#fff;
    position: absolute;
    top: 0;
    left: 0;
    border: 0;
    transform: scale(-1, 1);
}

.github-corner:hover .octo-arm {
                animation: octocat-wave 560ms ease-in-out
            }

            @keyframes octocat-wave {

                0%,
                100% {
                    transform: rotate(0)
                }

                20%,
                60% {
                    transform: rotate(-25deg)
                }

                40%,
                80% {
                    transform: rotate(10deg)
                }
            }

            @media (max-width:500px) {
                .github-corner:hover .octo-arm {
                    animation: none
                }

                .github-corner .octo-arm {
                    animation: octocat-wave 560ms ease-in-out
                }
            }